Paléogéographie et évolution géodinami que de la Bulgarie Septentrionale au Néogéne

E. Kojumdgieva, N. Popov. Paleogeography and geodynamic evolution of Northern Bulgaria during the Neogene. The paleogeographic evolution of Northern Bulgaria had 4 stages: l. Early Miocene; 2. Middle Miocene – Early Sarmatian; 3. Middle-Late Sarmatian; 4. Maeotian – Pliocene. The greatest part of Northern Bulgaria westward from the Diagonal Swell in Early Miocene was a plain, dipping towards the Carpathian Foredeep, with river valleys running into the latter. A brief marine ingression left traces in the valley of Paleo-Brâšljanica river. Two depressions were formed in the Middle Miocene: Varna-Balčik depression in North-Eastern Bulgaria and the longitudinal Miocene depression in North-Western Bulgaria. The formation of the latter was probably related to the compression of the blocks behind the Carpatho-Balkan arc, moving to the NE after Balla. The Fore-Carpathian basin in North-Western Bulgaria and the Euxinian basin in the North-Eastern Bulgaria occupied the depressions and its borders. The Middle Miocene – Early Sarmatian depressions during the Middle-Late Sarmatian were filled up with sediments and diappeared, but a new one (Lom depression) formed in the North-Western Bulgaria, probably by concentric extension derived from the active pressing of the Southern Carpathians. This depression existed also in the Maeotian-Pliocene interval, but was gradually filled with sediments. The Maeotian-Middle Pontian basin covered only the depression and its borders, but the Late Pontian-Pliocene transgression covered the Rumanian part of the Moesian plate and the Ruse – Silistra band of North-Eastern Bulgaria.